Short-Duration Exposure and the Transmission of Rhinoviral Colds

Abstract

Transmission of infection with rhinovirus type 55 was attempted under natural circumstances of interaction among 26 experimentally infected donors and 33 antibody-free (titer, <1:3) recipients. In a total of three experiments, only two recipients (6%) became infected. In the first experiment no transmissions from five donors to nine recipients occurred after 2–3 hr of loud vocalization and card playing in a small room. In the second experiment a cold was transmitted to one (9%) of 11 recipients living in dormitory rooms for 36 hr in groups consisting chiefly of two donors and two recipients. In the third experiment one (8%) of 13 recipients was infected after kissing an infected donor. In studies with rhinovirus type 16, the 50% human infectious dose was found to be 0.28 TCID₅₀ (50% tissue culture infectious dose) in the nose, 2,260 TCID₅₀ on the tongue, and 11,000 TCID₅₀ on the external nares. Rhinoviral infections are difficult to transmit by short-term natural exposure, perhaps because the agent must be present in overwhelming numbers to reach susceptible mucosal cells.